Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.53	12.142%	$171.0502	$171.05	$171.05	$171.10
Purchase #2	$18.29	6.166%	$19.4178	$19.42	$19.40	$19.40
Purchase #3	$101.59	3.526%	$105.1721	$105.17	$105.15	$105.20
Purchase #4	$8.84	13.332%	$10.0185	$10.02	$10.00	$10.00
Purchase #5	$45.76	3.337%	$47.287	$47.29	$47.30	$47.30
Purchase #6	$36.75	13.145%	$41.5808	$41.58	$41.60	$41.60
Purchase #7	$128.58	5.821%	$136.0646	$136.06	$136.05	$136.10
7 purchase totals =	$492.34		$530.5910	$530.59	$530.55	$530.70